As we know that when a charged capacitor is connected across a resistor then its voltage will decreased
This is known as discharging of capacitor
as we know that the equation of discharging is given as
[tex]V = V_0 e^{-t/\tau}[/tex]
here we know that
[tex]V = 2.8 Volts[/tex]
[tex]V_0 = 12 volts[/tex]
t = 3.90 s
now from above equation we have
[tex]2.8 = 12 e^{-3.90/\tau}[/tex]
[tex]ln(\frac{2.8}{12}) = -\frac{3.90}{\tau}[/tex]
as we know that
[tex]\tau = RC[/tex]
[tex]1.45 = \frac{3.90}{RC}[/tex]
[tex]1.45 = \frac{3.90}{3.60* 10^6*C}[/tex]
[tex]C = 0.75 * 10^{-6} F[/tex]
so capacitance is 0.75 micro farad
